import React,{Component} from "react";export default class RefCallback extends Component {    render() {        return (            <div>                <input ref={ c => this.input3 = c} type="text" placeholder='点击提示信息'/>                <button onClick={this.showData1}>点我提示左侧数据</button>                <input onBlur={this.showData3} ref={c => this.input2 = c} type="text" placeholder='失去焦点提示信息'/>            </div>        )    };    showData1 = ()=> {        const {input3} = this        alert(this.input3.value)    };    showData3 = () => {        const  {input2} = this        alert(input2.value)    }}